Nur Aidawaty Rafan

Extensive Tracking Performance Analysis of Classical Feedback Control for XY Stage Ballscrew Drive System

Performance analysis in term of identifying the systems transient response, stability and systems dynamical behavior in control system design is undeniably a must process. There are several ways in which a system can be analyzed. An example of well known techniques are using time domain and frequency domain approach. This paper is focused on the fundamental aspect of analysis of classical feedback controller in frequency domain of XY milling table ballscrew drive system. The controller used for the system is the basic PID controller using Matlab SISOTOOL graphical user interface. For this case, the frequency response function (FRF) of the system is used instead of using estimated model of transfer function to represent the real system. Result in simulation shows that after proper tuning of the controller, the system has been successfully being controlled accordingly. In addition, the result also fulfill the set requirement of frequency domain analysis in terms of the required gain and phase margin, the required maximum peak sensitivity and complimentary sensitivity function and the required stability.

Theoretical Analysis of Friction Compensation Using Sliding Mode Control

Friction is an undesired nonlinear phenomenon that reduces position and tracking accuracy in machine tools application. This paper focuses on development of control technique to compensate friction force at motion reversal of a drive system that generates quadrant glitch phenomenon thus improving tracking accuracy. Sliding Mode Control (SMC) is designed to compensate friction. The Generalized Maxwell-Slip (GMS) friction model is applied for numerical analysis. The performance of the controller is analysed based on the reduction in the quadrant glitches magnitude. The performance of the SMC controller is compared with the classical PID controller. Results show that SMC controller yields the smallest quadrant glitch magnitudes.

Theoretical Analysis of Velocity and Position Loop Behaviour of Nonlinear Cascade Feedforward Controller for Positioning of XY Table Ballscrew Drive System

The trend in machine tools and positioning systems nowadays are demanding for accuracy, precision and robustness attributes. In addition to those characteristics, a low-cost and adaptive control systems towards various disturbance forces also add a significant advantage to control engineers who can fulfill those needs. The objective of this paper is to introduce a newly improved control strategy named as Nonlinear Cascade Feedforward. It is basically, a cascade control structure with the additional of two add on modules called Nonlinear function plus independent feedforward function. Secondly, the aim of this article is to focus on the fundamental aspect on how to analyze the open loop and closed loop behavior for both velocity and position loop in the control structure by extracting the mathematical formulation of the controller. The outcome from this paper which is in the form of mathematical formula is beneficial and exceptionally significant during the validation and verification stage. The theoretical analysis involved are analysis on gain and phase margin, bandwidth frequency, sensitivity function, position error and finally analysis on dynamic stiffness of the system which is in this case the XY Table Ballscrew drive system. The strength of this controller is the self-adjusting mechanism towards variable disturbance cutting forces. Based on mathematical formulation, it is observed that the designed nonlinear cascade feedforward offer more flexibility and robustness in terms of the ability to compensate the tracking errors at variable disturbances.

An Enhancement in Control Laws of Super Twisting Sliding Mode Servo Drive Controller Using Hyperbolic Tangent Function and Arc Tangent Smoothing Function

Super Twisting Sliding Mode (ST-SMC) controller belongs to a class of controller known as Sliding Mode Control (SMC). SMC is widely known as a robust controller and has been shown in literature to be an effective medium for excellent control performance especially regarding disturbance force rejection. However, the control performance of SMC is often affected by chattering phenomenon thus reducing the applicability of SMC as position controller of choice in machine tools application where chattering induced vibration cannot be tolerated. ST-SMC is constituted as a higher order SMC. This paper explores control performances of ST-SMC in term of chattering reduction by introducing two types of switching functions in the control laws of the controller; namely, a hyperbolic tangent function (HST-SMC) and an arc tangent function (Arc-ST-SMC). The control performances are analysed based on reduction in magnitude of the tracking error (RMSE) and reduction in magnitude component of the chattering elements observed in frequency domain. The optimized ST-SMC produced the best tracking performance but chattering effect is still persistent. In comparison, HST-SMC produced a comparable tracking performance to ST-SMC with minimal difference of only 12.5% (RMSE). HST-SMC offers a fair trade-off between tracking accuracy and chattering attenuation. On the other hand, arc-ST-SMC produced the most reduction in chattering.

Parameter Properties of a Sliding Mode Controller Design in Friction Compensation

An optimized controller provides consistent performance with high accuracy and precision even in the presence of disturbance forces. Disturbance forces can be a cutting force or friction force or both. Tracking performance of a drive system is critically influenced by the mechanical structure, disturbance forces and work piece mass. Sliding mode controller is designed to compensate disturbance forces especially friction. This paper presents parameter tuning strategies in designing a sliding mode controller in compensating a nonlinear friction behaviour occurred in machine tools application. The main parameter properties of a sliding mode controller are identified and analyzed. The proposed methods are analytically designed and numerically validated by variability index performance. The result analysis is presented by comparison of tracking position errors of linear motion using proposed methods with lower variability index. The result shows that method a with approach b has lower tracking position error and lower variability index, hence a better chattering effect and tracking position error performance.

Design of super twisting sliding mode control for single axis direct drive motor

Chattering effect is often associated negatively with the application of the robust nonlinear sliding mode control. This paper compares the tracking responses of system controlled with different controllers and demonstrates the ability of super twisting sliding mode control in chattering suppression and enhancement of tracking performance against classical controller and traditional sliding mode control. The controller was numerically analyzed and experimentally validated on a direct drive single axis positioning system which is described as a second order single-input-single-output system. Three controllers, namely; PID, pseudo sliding mode control and super twisting sliding mode control were designed, analyzed and compared. A Kalman-Bucy filter was designed for velocity estimation to reduce noises from numerical differentiation of position measurement. Results showed the superiority of super twisting sliding mode controller in smoothing the control input and suppressing the chattering effect compared to pseudo sliding mode control. Additional investigation was performed by replacing the signum function using a hyperbolic tangent function. However, only slight improvement in tracking performance was recorded. The results displayed the novelty of super twisting algorithm in chattering suppression making it an attractive option for real-time application.

Investigation on Tracking Performance of Adaptive Friction Compensation Using Cascade P/PI Controller at Low Velocity

Tracking performance of drive systems is one of the factors that contribute to the accuracy of a machine tool. Tracking error which is much related to non-linear friction behavior of the system, is analyzed based on sliding and pre-sliding regime in terms of quadrant glitches that occurred in reversal velocity. In pre-sliding regime, friction forces is described while axes moving at low velocity. Friction compensation model is therefore a need for accurate motion control applications. This paper analyzes experimentally the performance of two different friction compensation model based namely Generalized Maxwell Slip (GMS) and Sigmoid like curve function (SLCF) model. The experiment validation is performed in a circular motion tested at a ball screw driven XY table controlled by cascade P/PI controller feedforward. The experimental results indicates that SLCF friction model based feedforward capable to reduce magnitude of quadrant glitch that lead towards better tracking performance in machine tools application.

Theoretical Analysis of Close Loop Behaviour of Ideal Cascade Controller Structure for Positioning of XY Table Ballscrew Drive System

The implementation of Classical Cascade Controller for the purpose of controlling various type of engineering appliances has been vastly utilized by control engineer community. Cascade controller provides a simple structure of controller but yet functional and have the ability to satisfy the control design requirement. In general, the controller consists of two loops, namely velocity loop and position loop. This paper is focused on the fundamental aspect on how to analyzed the close loop behaviour for both velocity and position loop and to extract the mathematical formulation of the controller. The outcome from this paper which is in the form of mathematical formula is useful and very significant in order to validate the theoretical result with the simulation result. To be more precise, the result from this research work are in the form of transfer function for both velocity and position loop of the position output, position error, dynamic stiffness of the controller and the damping ratio of the system which is in this case the XY Table Ballscrew drive system.

Spectral Analysis of Cutting Forces Data for XY Table Ballscrew Drive System

. The utilization of spectral analysis for the purpose of investigating machining parameters in frequency domain has been widely practiced by group of researchers in engineering field. In this case the machining parameters involved are the cutting force parameter. By adapting spectral analysis to the cutting forces data, the researcher will have the access to identify the specific cutting forces exerted to the surface of the workpiece at each particular frequency under a set of frequency content. This paper is paying attention on the essential aspect on how to analyze the cutting forces data appropriately. It is recommended that those data need to be transformed first from the original form of cutting force data in time domain into the form of cutting force data in frequency domain. The outcome from this paper is in the form of graphical representation of cutting force data in frequency domain. It is obtained by applying Fast Fourier Transform (FFT) technique. To be more clear-cut, the result from this research work shows that the cutting force is directly proportional to the depth of cut and inversely proportional to the spindle speed of the end mill machine. The cutting force data later on will be used as an input disturbance for XY table ball screw drive system during the simulation process in the Matlab simulink diagram.